Fuel supply system with emergency switching means



May 19, 1953 F. H. CAREY. I 3

' rum. SUPPLY svs'nzu WITH. EMERGENCY swncx-xmc MEANS Filed Jan. 1-4, 1948 4 Sheets-Sheet 1 INVENTOI? By 648E) W 2F &.4, ATTORNEY.

May 19, 1 953- I F. H. CAREY 2,638,973 FUEL SUPPLY SYSTEM WITH EMERGENCY swncnmc MEANS Fil ed Jan.- 14, 1948 .4 Sheets-Sheet 2 BY Wu F M ATTORNEY:

May 19, 1 953 Fl HIC-AREY- 5 5 FUEL SUPPLY smm WITH macsncv swrrcnmc mamas Filed Jab. 14, 1943- I 4 sheets-sheet :5

INVENTOR BY ff 6. 61985),

ATTORNEYS May 19, 1953" F. H, CAREY FUEL SUPELY SYSTEM WITH EMERGENCY SWITCHING MEANS Filed Jan. 14', 1948 4 Sheets-Sheet 4 nvvavroe F. M $065 7 ATTM Patented May 19, 1953 FUEL surety S$TEM WITH .swnonme FrederickHenrwGarey, Cheltenhamflilngland asr Slgflfll to Dmzvty Equipment L mite fl ile ll i ham, En nd Application 3anuary-14, 1 951 8, Serial No.2;342

InGrea't Britain Deoembfl :24, 1194'] This invention relates to liquid fuel supply systems for aircraft continuous combustion gas turbines having burners of the spill type, and comprising essentially -two pumps of which lone, a eireulatingpum-p, operates normally as a fixed -cieli-very unit *to circulate fuel in a vcircuit inol-uding the burners and. the other, a supply 'pump, operates normally as a variable delivery unit to inject fuel into the circulating flow as necessary -*to maintain a required engine speed or to -efleot any change thereof. A sspi-ll tylpe hurner is herein :defihedvas a burner in \whioh, except during certain operating ..conditions, only :a proportion of the fuel supplied :to 1thei buhner passes out through the burner (discharge .orifioe and the remainder passesibacl; along a return line. Such a system is hereinafter referred to as a system as hereinspeoifiedz The 3 present invention seeks -:to :provide an 11111- proved arrangement ,in such -=a system, whereby it -ispossib1e to maintain ianiadequate emergency fuel *supply from one pump, thus avoiding loomplete ia'ilure of the system "in the event of failure 'of either pump, and to this :emi :and tin lacnordanee with the invention, :the normally fixed delivery circulatingpumpus capahlesoi :emergenoy operation as a wariable delivery unit, and :means are provided whereby failure of either 'Ipump results in-emergency operation of ;the still operative pump to deliver :fuel irom the tank 1130 the burners. During emergenoy operation :the return line from the burnersmwould. ordinarily be closed, and (the burners would aiunetion as simple clirect+injection :burners so :long iassthe emergencylcontinues.

:In defining the lsystem with awhioh the lint-ention is concerned, :the circulatin ppm-Dis zstate to operate -.normally1as.-a fixed 'deliveny unit. :It ,is --,coneei-vable :to wary the .yoperation :of 'sthe {cirmulating pump :without interfering with :lihe basic :principle f the system, for instance by simultaneously inversely varying the traction ;of 1the.-supplyipumpendiit is be iunderstqodfthat sth viinvention lcovees such finer-atten- :In order that ithe in ention ma Gee me 2016813157 rundezstoogl and readily wcarried in-to efifefltnfi systemdnaeeorflam t-h ew t 1 L.v zbezsieserib b new o examp e 11 1 s to the .eccpmn n ing fliae emmatlc drawings 19 whim:

lfili ure )1 zeh ws th sys em w th {the ream-n nents in a position for normal operati e fi u e amete/ems iq e atie @With :th eup l eum havin fai ed;

liguree hows t 'emet ne .qnere iqn-wit eth eimulet i pum h ving :iai si; and

QeQlaimsmisfi 6th 2 figure A shows a -.detail modifiqaztion ,oi the system of figure 1,

lithe .basic principles of the :system, and the form vand manner of operation of the individual 5 burner nozzles, are disclosed in :some getail in the copending iapplioation, ,Semial No. 2343,,fi1ed lcoinoidentally ghe'rewith, mow Patent No. 2,608,247 issuedAug'u-st 26, 1952.

Referring to Figure '1 herein, :the basic system .openates during normal running in the zfollowing manner. A anemia-ting pump 5 @riilen by "the engine openates Has a fixed de ivery pu and icircula-tes iuel .around a circuit defined by 1a first cfinduit means including th tp mp,.. iiseharge line :Sal, ,a purnersupply line 2, .12; -hurner ring 6, :burners a4 ttonly zone .of ewhiqh is shown) .a -collector ring 5, return sline L6, and hump suemien zline M. .A supply hump .sl whiqh :is also engine ,elriven operates .ias a variable {del ve y pum'p and withdraws fuel-lbs! silay f 311116185 from a su ly {tank 8 and lpasses it throu h a upply :line fl including ,a metering valve orthrottle 0W, to inject ifuel sin-to the circulating flow at a tconvenient Junction fpoint A16 in the return dine :6 running ifrqm the bur-me. :rin :5 to the in e of the .circulating :pump $1. The lines 18;! and :9 geonstitutera second conduit means.

*fiihe mire-mating :and sunplmpumps ar of simsila desi n and ea h QQ JlDIZiWS 1a m nia 9x 1 ner ass mbly 12' fl 'q nistqns 12 sQQnStr-aihed to wreemrp ate zl i hjin 1?: t s nine 4 3 the eceentrimty o which with nesne :120 t ra ia rlinqe essexn i i1 Q 3Pm$ th love et y st o Q- the i ini i e t ack ne 1 1? sp in 9 L i wa ds e-P s 1; i m-ie sm zi itws i lei eklr i m .ip imeer *5 si i: "has a pr ss la 11 2") *r eneqti sly e on ti -a P su -;cQntrQ1 i-ns the m sitio 40 the p1un er T mum s {I nd J (a e also aqhr i tim w c isle elq zsent zi usa pressu e w thin the sp :hetw en th wean n 13 an e e tin 12 h, sy em a so inc ude a 41 mm t ntr Maw? 'n8rli t l lmiilt mi o #2 ,11 e 9 aaisoletie walval a eme ieensz qen m wai all, and ri ne eturr a li E2 an -H il -th hur su n l ne 2 endl atinn in h ,r s eetiye ilh r s a so shQ'W' -i itsfq en n si ien a la pr ssur coc Whentne s stems ;f, ,n.;qt' ins n9 el yla shown ,Fi il t :1 $1 8 @Efififilllfi I aqe 1120f th 55 slugge A; p m simulat n mama I ,ieihraus the t ench lin an th Pa sa e .25 o th 3 emergency control valve 22, exposed merely to the pressure of fuel within the tank 8 with the result that the spring I6 is able to maintain the track ring I3 of this pump I permanently in a position of maximum eccentricity so that the circulating pump functions normally as a fixed delivery pump. The pressure face I! of the plunger I of the supply pump 1 is exposed by way of the line 4| to the supply pump delivery pressure and the supply pump I thus accommodates itself to variations in the setting of the metering valve IE) to maintain a constant pressure of fuel in its supply line 9. Thus, when the metering valve I9 is moved to restrict the fiow through the valve, the pressure in the line 9 between the valve and the pump I, and hence in the branch line 4I, tends to rise with the result that the plunger I5 of the supply pump moves against its spring I6 to reduce the stroke of the pump until the original pressure in the line 9 is reached. Also, in the normal running condition, a spring 28 maintains the movable element 21 of the emergency control valve 22 in the position shown in Figure l, and likewise a spring 30 maintains the movable element 29 of the isolating valve 2| in the position shown. Flow in the supply line 2 to the burners maintains the non-return valve 23 open to permit such flow, and the non-return valve 24 is similarly opened by the return flow in the line 6.

The pumps are generally designed so that there can be no major failure unless it be interruption of the actual drive of the pmnp, for

example through a coupling which is shearedby overload. Let it be assumed that for some reason the supply pump I fails, and in order to represent that condition it has been omitted from Figure 2. In that condition the supply pump must be isolated from the system, which in fact occurs automatically. It will be seen that the multi-pistoned member 29 of the circuit control valve is subjected at its opposite ends (by way of pressure lines 44 and 45) to the centrifugal pressures developed within the respective pump casings I and I, the lower end of the member 28 being exposed via line 44 to the centrifugal pressure in the circulating pump I and the upper end via line 45 to the centrifugal pressure in the supply pump I. The area exposed to supply pump pressure is somewhat greater than that exposed to circulating pump pressure, and this, plus gravity, biases the piston member 29 into the normal position of Figure 1. Failure of the pump I means a cessation of the centrifugal pressure in its casing with the result that the piston member 29 of the cir cuit control valve moves up from the position shown in Figure 1, under the influence of circulating pump centrifugal pressure via line 44,

to an emergency position shown in Figure 2. A spring (not shown) may be used to assist in its raising. Directly this happens, fuel delivered by outlet line 3! from the circulating pump I can no longer pass by way of burner supply line 2, but does pass through the circuit control valve I9 and through the line 32 and branch line 33, to shift the plunger I5 of the circulating pump I in a manner to alter the pumps normal delivery rate. The pump I will then function as a variable delivery unit in exactly the same way as did the supply pump 1 prior to its failure. Pressure in the line 32 also shifts the movable element 27 of the emergency control valve 22 to the position shown in Figure 2 (the passage 26 containing a sufiicient restriction that this element will move to the right in opposition to spring 28) at which it breaks communication between line 42 and the pressure face II of plunger I5, but permits fuel to reach the pump I by way of line 42, the circuit control valve I9, and line 43, for delivery by way of line 3|, circuit control valve I9, line 32, and lines M and 9 to and through the metering valve In to junction point 96, and along the return line 6 as far as the non-return valve 24, which now closes. Flow also occurs along a branch line 34 leading to the isolating valve. Flow in the line 34 raises the member 29 of the isolating valve against the spring 39 to permit the fuel to flow through a by-pass 35 and through passages 36 within the member 29. The fuel issuing through the isolating valve closes the non-return valve 23 (the line 2 being also closed off at the circuit control valve I9) and flows along the remainder of burner supply line 2 to feed the burners 4. The system now functions on the circulating pump only, the delivery whereof is variable under the influence of de livery pressure applied at I I by way of line 33, as already described, and the burners function as simple direct-injection burners (the burner return line I5 being closed by the valve 24). The conduit sections 42 from the reservoir to the intake side of the circulating pump I (by Way of the circuit control valve I9), 32 from the output side of the circulating pump (by way of the circuit control valve) to and past the emergency control valve 22 and thence by conduit section 4! to the output side of the supply pump I, for connection to the second conduit means in advance of the throttle means Ill, and the branch conduit 34 off the second conduit means to the burner supply line 2 ahead of non-return valve 23, may be considered a third or emergency conduit means. The isolating valve 29 is included therein, and that portion of the second conduit means which includes the throttle means In may be considered as included also in the third conduit means. The third conduit means also branches, in the vicinity of the emergency control valve, to place the plunger I5 and its face II of the delivery-varying means of the circulating pump I under the influence of delivery pressure for automatic control when, under emergency conditions, only the circulating pump is operating.

Had it been the circulating pump which failed, which condition is represented by its omission in Figure 3, the delivery pressure from the circulating pump would fall and the element 29 of the isolating valve which is exposed at its upper end to such pressure would be lifted by the action of the delivery pressure from the supply pump in the branch line 34, acting always on its lower end, and the supply pump would then feed the burners through the isolating valve 2I, at the same time closing the non-return valve 23 by way of pressure acting through lines 9 and Ia. The absence of flow in the return line 6 due to the failure of the circulating pump would permit the supply pump to deliver thus along the line 6 to close the non-return valve 24. The system now functions with the supply pump alone, still acting as a variable-delivery pump, and with the burners operating as simple direct-injection burners.

In the modification shown in Figure 4, in which the same reference numerals are used to denote similar parts, the circulating and supply pumps 31 and 38 respectively are each of the'fixed disvariations in the pressure in the second conduit means as determined by the throttle valves setting; a second delivery-controlling duct leading from the pressure side of the circulating pump, past the circuit control valve, to that pumps delivery-varying means, to regulate automatically the circulating pumps delivery, but the circuit control valve being arranged to close said second delivery-controlling duct so long as said circuit control valve remains in its normal operating position, and to open said second delivery-controlling duct upon shifting to its emergency operating position; a branch duct from said second delivery-controlling duct to said emergency control valve, to apply the pressure of the circulating pump to the emergency control valve to open the latter upon shifting of the circuit '"control valve to its emergency operating position; an interconnecting duct extending between the emergency control valve and the first delivery-controlling duct, the emergency control valve being arranged to close said interconnecting duct so long as the emergency control valve remains in its biased, normal operating position, but adapted to connect the pressure side of the circulating pump with the second conduit means in advance of the throttle valve by way of the first delivery-controlling duct upon shifting of the emergency control valve from its biased normal operating position; and a third, by-pass conduit means connecting the second conduit means, beyond the throttle valve from the supply pump, with the first conduit means in advance of its connection to the burner, the normally closed isolating valve being interposed in said third conduit means and arranged to be opened by fuel under pressure as supplied by way of said third conduit means.

5. A fuel supply system as in claim 4, including a non-return valve in said first conduit means, at the opposite side of the connection to the latter of the third conduit means from the burner, arranged to permit circulation in the first conduit means during normal operation but to prevent reverse fiow in the first conduit means during emergency operation.

6. A fuel supply system as in claim 4, including a non-return valve in said first conduit means, intermediate the burner and theintake side of the circulating pump, arranged to permit return flow from the burner during normal operation but to block reverse fiow, the second conduit means being connected to the first conduit means at a point intermediate said non-return valve and the intake of the circulating pump.

'7. A fuel supply system as in claim 6, and a second non-return valve in said first conduit means, intermediate the delivery side of the circulating pump and the point of connection to said first conduit means of the third conduit means, said non-return valves being arranged to permit one-Way circulation in the first conduit means during normal operation but to block reverse fiow during emergency operation.

8. A fuel supply system as in claim 4, wherein each of the circulating and supply pumps is of the variable displacement type, and its deliveryvarying means includes a stroke-controlling element, and wherein the first and second deliverycontrolling ducts are connected to the respective stroke-controlling elements to shift the latter under appropriate operating conditions, as defined in claim 4, for variation of the delivery of the corresponding pump.

9. A fuel system as in claim 4, wherein each of the pumps is of the fixed displacement type, and wherein the delivery-varying means is constituted by a by-pass and valve normally operatively associated with the supply pump, and connected in the second conduit means, the interconnecting duct constituting part of the third conduit means and being arranged to connect said by-pass and valve to the first conduit means.

FREDERICK HENRY CAREY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,970,380 Horsel Aug. 14, 1934 2,366,388 Crosby Jan. 2, 1945 2,440,371 Holley, Jr. Apr. 27, 1948 

